Finite element modeling approaches and comparative study on the nonlinear behavior of steel shear-links

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2013
Kızıldağ, Yaşam
This study deals with the finite element modeling of the nonlinear behavior of shear links under various loading and boundary conditions. Shear-links are the most important part of an eccentrically braced steel frame system, and provide fuse in terms of reducing the forces acting on the rest of the members such as columns and braces in the framing system. Shear-links are designed for dissipation of large amounts of energy in case of overloading; therefore construction of buildings with eccentrically braced frames is suitable for earthquake resistant design. Since strength, stiffness and ductility characteristics of shear links dominate the behavior of eccentrically braced frames, having full knowledge of the behavior of shear-links is an important research topic. The early research on eccentrically braced frames in literature were generally based on experimental studies that were costly to conduct, but nowadays the use of advanced finite element software packages provide opportunity for the assessment and simulation of the nonlinear behavior of shear-links under various loading and boundary conditions. Such a study has been undertaken in this thesis, and the shear links are modeled and analyzed in finite element program ANSYS Workbench with 2-D and 3-D elements. First, a verification study is conducted, where shear-links from past experiments are considered and the results obtained from the analysis are compared with experimental data. The shear links are modeled according to the original dimensions and boundary conditions. The material properties are calibrated based on the cyclic behavior of steel with some assumptions that are described in detail in the thesis. After this verification study, a detailed comparative finite element study has been conducted. In this part of the thesis, the links are analyzed not only with the proposed finite element modeling approach, i.e. the utilization of 2-D and 3-D elements and cyclic calibration of steel material through the use of ANSYS Workbench, but also with a frame element that can capture spread of plasticity both along element length and section depth. In the first part of the comparative study, the contribution of flange to the overall shear force carrying capacity of shear-links is assessed through both finite element modeling approaches. With this comparison, a realistic description of flange shear strain for the frame finite element model is suggested. In the second part of the comparative study, the influence of unsymmetrical loading protocols on the nonlinear behavior of shear-links is studied through the use of both finite element modeling approaches, and the results are compared to each other and the accuracy of the frame finite element model is assessed.
Citation Formats
Y. Kızıldağ, “Finite element modeling approaches and comparative study on the nonlinear behavior of steel shear-links,” M.S. - Master of Science, Middle East Technical University, 2013.